Tweak HTTP code to always sleep.

Check explicitly for the 'no channels' case and
sleep instead, to avoid busy-waiting. (This is a work-
around, the underlying issue still be be traced)

simgear/io/HTTPClient.cxx

@@ -645,9 +645,13 @@ void Client::setMaxConnections(unsigned int maxCon)
 
 void Client::update(int waitTimeout)
 {
-    d->poller.poll(waitTimeout);
-    bool waitingRequests = !d->pendingRequests.empty();
+    if (!d->poller.hasChannels() && (waitTimeout > 0)) {
+        SGTimeStamp::sleepForMSec(waitTimeout);
+    } else {
+        d->poller.poll(waitTimeout);
+    }
     
+    bool waitingRequests = !d->pendingRequests.empty();
     ConnectionDict::iterator it = d->connections.begin();
     for (; it != d->connections.end(); ) {
         Connection* con = it->second;

simgear/io/SVNRepository.cxx

@@ -73,7 +73,8 @@ public:
     
     void updateFailed(HTTP::Request* req, SVNRepository::ResultCode err)
     {
-        SG_LOG(SG_IO, SG_WARN, "SVN: failed to update from:" << req->url());
+        SG_LOG(SG_IO, SG_WARN, "SVN: failed to update from:" << req->url()
+            << "\n(repository:" << p->baseUrl() << ")");
         isUpdating = false;
         status = err;
     }

simgear/io/sg_netChannel.hxx

@@ -123,6 +123,8 @@ public:
     void addChannel(NetChannel* channel);
     void removeChannel(NetChannel* channel);
     
+    bool hasChannels() const { return !channels.empty(); }
+    
     bool poll(unsigned int timeout = 0);
     void loop(unsigned int timeout = 0);
 };